Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$58.50	4.842%	$61.3326	$61.33	$61.35	$61.30
Purchase #2	$33.94	10.146%	$37.3836	$37.38	$37.40	$37.40
Purchase #3	$80.98	11.619%	$90.3891	$90.39	$90.40	$90.40
Purchase #4	$226.83	4.186%	$236.3251	$236.33	$236.35	$236.30
Purchase #5	$186.93	11.870%	$209.1186	$209.12	$209.10	$209.10
Purchase #6	$35.60	12.581%	$40.0788	$40.08	$40.10	$40.10
Purchase #7	$223.36	6.104%	$236.9939	$236.99	$237.00	$237.00
7 purchase totals =	$846.14		$911.6217	$911.62	$911.70	$911.60